An analysis of trading ratio for water pollution control trading systems using a geographic information system and the finite segment method

Nitrogen from non-point sources reacts with the environment during flow to the waterway. These reactions cause decay of the pollutant. There is a question regarding whether pollution trades between point sources and non-point sources that involve nitrogen should consider this decay. The failure to consider this decay may cause trades to fail to achieve their environmental goal or to inefficiently achieve their environmental goal. Additionally, planners may consider the decay to target reductions and improve efficiency of trading programs. The dissertation uses a geographic information system (GIS) and the finite segment method to evaluate the need for the use of a trading ratio to consider decay. It uses GIS, principles of process engineering, and principles of hydrology to model the distribution of the nitrogen in the watershed with and without decay. Additionally, it compares the predictions of the concentrations with and without decay. Finally, it uses GIS to estimate appropriate values of trading ratio. The results show that the effect from decay during overland flow is appreciable but not always significant. The appropriate values of trading ratio are likely to be less than 1.3. Use of trading ratio may protect environmental quality and improve the efficiency of pollution control. However, sometimes the values of trading ratios are small relative to other factors so that the use of trading ratio is inconsequential. Finally, planners may use the decay of nitrogen from non-point sources to target the locations of the reductions to achieve the maximum decrease of concentration or to achieve the maximum increase of load without an increase in concentration